Aircraft are commonly equipped with a fuel supply system that draws combustion fuel from a fuel source (e.g., a storage tank) and supplies it to a propulsion engine, such as a gas turbine engine. A representative fuel supply system includes a metering valve, a supply pump fluidly coupled between the metering valve and the fuel source, and a bypass valve fluidly coupled between the inlet and the outlet of the supply pump. The supply pump may be, for example, a fixed displacement pump that is mechanically coupled to a spool of the gas turbine engine. During operation, the supply pump provides combustion fuel to the metering valve, which meters the fuel in accordance with commands received from an engine controller. The metered combustion fuel is directed into the fuel manifold of the aircraft engine, mixed with air, and ignited to drive one or more engine turbines and to produce forward thrust. The bypass valve redirects excess fuel provided by the supply pump outlet back to the supply pump inlet.
In addition to the above-described components, an aircraft fuel supply system may further include a pressurizing valve fluidly coupled between the fuel metering valve and the aircraft engine. When the fuel pressure upstream of the pressurizing valve is undesirably low, the pressurizing valve impedes fuel flow to the aircraft engine to maintain fuel pressure upstream of the pressuring valve and downstream of the supply pump (e.g., at the supply pump outlet) above a predetermined minimum pressure, such as 250 pounds per square inch (psi). By maintaining the back pressure above a predetermined threshold in this manner, the pressurizing valve helps to ensure that pressure-sensitive components downstream of the supply pump (e.g., fuel-conducting servomechanism of the type described below) operate effectively and efficiently.
In addition to supplying combustion fuel to an aircraft engine manifold, an aircraft fuel supply system may also supply fuel to one or more fuel-conducting servomechanisms (“servos”). These servos perform various functions aboard the aircraft and may include, for example, a variable-geometry servo, a bleed air servo, and a metering valve actuator servo. The operation of such servos may be negatively impacted if the pressure of the fuel supplied thereto surpasses a maximum pressure. Thus, to prevent the pressure of the fuel supplied to the servos from surpassing a maximum pressure threshold, a pressure regulating valve may be disposed between the fuel supply system pump and the control servos. During operation, the pressure regulating valve selectively impedes fuel flow to maintain the pressure of the fuel supplied to the servos below a predetermined maximum pressure, which may be, for example, 300 psi.
It should thus be appreciated that aircraft fuel supply systems of the type described above commonly employ two separate pressure regulating devices; i.e., a pressurizing valve that maintains fuel pressure at supply pump outlet above a predetermined minimum pressure, and a pressure regulating valve that maintains a downstream fuel pressure (i.e., the pressure of the fuel supplied to one or more servos) below a predetermined maximum pressure. Each pressure regulating device generally includes a separate valve housing (e.g., a sleeve), valve element (e.g., a piston), spring, mounting hardware, and so on. As a result, the utilization of two independent pressure regulating devices negatively impacts the overall part count, cost, weight, and envelope of the fuel supply system.
Accordingly, it is desirable to provide a unitary and compact valve capable of performing both pressurizing and pressure regulating functions. It would also be desirable to provide a fuel supply system suitable for deployment on an aircraft that employs such a pressurizing and pressure regulating valve. Other desirable features and characteristics of the present invention will become apparent from the subsequent Detailed Description and the appended claims, taken in conjunction with the accompanying drawings and this Background.